1. Field of the Invention
The present invention relates to a uni-morph, bi-morph or other types of piezoelectric or electrostrictive actuator which undergo displacement in the form of bending, deflection or flexure and which can be used for ink jet print heads, microphones, sounding bodies (such as speakers), various transducers and other components or devices. The term "actuator" used herein is an element or member capable of transducing or converting an electric energy into a mechanical energy, i.e., a mechanical force, displacement or strain.
2. Discussion of the Prior Art
In recent years, an element whose displacement can be controlled has been widely used and increasingly demanded in the fields of optics and precision positioning or machining operations, for example, for adjusting or controlling an optical path length or the position of a member or component of a device, on the order of fractions of a micron (.mu.m). To meet this need, there have been developed various piezoelectric or electrostrictive actuators utilizing a piezoelectric or electrostrictive material such as a ferroelectric material, which exhibits the reverse or converse piezoelectric effect or the electrostrictive effect, in which such a piezoelectric or electrostrictive material produces a mechanical displacement upon application of a voltage or electric field thereto.
For example, an ink jet print head uses a piezoelectric/electrostrictive actuator of a conventional uni-morph or bi-morph type, which is required to permit a high-quality high-speed printing operation. To this end, developments have been made to reduce the size and required drive voltage of the piezoelectric/electrostrictive actuator, and improve the operating response of the actuator.
A piezoelectric or electrostrictive element of such an actuator is carried by a substrate, which functions as an oscillator or transducer plate. For assuring sufficient amount and force of bending or flexural displacement of the substrate or plate, it is important to reduce the thickness of the substrate, on the one hand. On the other hand, however, the reduction in the substrate thickness undesirably results in a decrease in the mechanical strength of the substrate.